Abrading – Machine – Combined
Reexamination Certificate
2000-05-17
2002-04-09
Eley, Timothy V. (Department: 3723)
Abrading
Machine
Combined
C451S288000, C451S446000
Reexamination Certificate
active
06368194
ABSTRACT:
TECHNICAL FIELD
The present invention relates to mechanical and chemical mechanical planarization of microelectronic substrates. More particularly, the present invention relates to controlling the pH of a microelectronic substrate during planarization and post-planarization processing of the microelectronic substrate.
BACKGROUND OF THE INVENTION
Mechanical and chemical-mechanical planarization processes remove material from the surfaces of semiconductor wafers, field emission displays, and many other microelectronic substrates to form a flat surface at a desired elevation.
FIG. 1
schematically illustrates a planarizing machine
10
with a platen or base
20
, a carrier assembly
30
, a polishing pad
41
positioned on the platen
20
, and a planarizing liquid
44
on the polishing pad
41
. The planarizing machine
10
can also have an under-pad
25
attached to an upper surface
22
of the platen
20
for supporting the polishing pad
41
. In many planarizing machines, a drive assembly
26
rotates (arrow A) and/or reciprocates (arrow B) the platen
20
to move the polishing pad
41
during planarization.
The carrier assembly
30
controls and protects a substrate
12
during planarization. The carrier assembly
30
generally has a substrate holder
32
with a pad
34
that holds the substrate
12
via suction. A carrier drive assembly
36
typically rotates and/or translates the substrate holder
32
(arrows C and D, respectively). Alternatively, the substrate holder
32
can include a weighted, free floating disk (not shown) that slides over the polishing pad
41
.
The combination of the polishing pad
41
and the planarizing liquid
44
generally defines a planarizing medium
40
that mechanically and/or chemically-mechanically removes material from the surface of the substrate
12
. The polishing pad
41
may be a conventional polishing pad composed of a polymeric material (e.g., polyurethane) without abrasive particles, or it may be an abrasive polishing pad with abrasive particles fixedly bonded to a suspension material. In a typical application, the planarizing liquid
44
may be a chemical-mechanical planarization slurry with abrasive particles and chemicals for use with a conventional non-abrasive polishing pad. In other applications, the planarizing liquid
44
may be a chemical solution without abrasive particles for use with an abrasive polishing pad. In any case, the planarizing liquid
44
can be pumped from a planarizing liquid supply
45
through a conduit
46
, and through orifices
43
to a planarizing surface
42
of the polishing pad
41
.
To planarize the substrate
12
with the planarizing machine
10
, the carrier assembly
30
presses the substrate
12
against the planarizing surface
42
of the polishing pad
41
in the presence of the planarizing liquid
44
. The platen
20
and/or the substrate holder
32
then move relative to one another to translate the substrate
12
across the planarizing surface
42
. As a result, the abrasive particles and/or the chemicals of the planarizing medium
40
remove material from the surface of the substrate
12
.
After the substrate
12
has been planarized, particulate matter, such as abrasive particles, particles removed from the polishing pad
41
, and/or particles removed from the substrate
12
may adhere to the substrate. Accordingly, the substrate
12
can be rinsed to remove the particulate matter before the substrate
12
undergoes additional processing. One conventional approach to rinsing the substrate
12
is to pump a rinsing solution
53
from a rinsing solution supply
54
through the orifices
43
to the planarizing surface
42
of the polishing pad
41
. The rinsing solution
53
rinses the substrate
12
while the substrate remains in situ on the polishing pad
41
. The rinsing solution
53
may be introduced to the polishing pad
41
as the relative velocity between the substrate
12
and the polishing pad
41
is reduced or ramped down.
Another rinsing approach, which can be used in addition to or in lieu of the in situ approach discussed above, can include removing the substrate
12
from the polishing pad
41
with a substrate transporter
60
and moving the substrate
12
to a rinse chamber
50
. The substrate transporter
60
can include a grasping device
62
that engages the substrate
12
after the substrate has been detached from the carrier assembly
30
. The substrate transporter
60
can further include one or more movable arms
61
that can robotically move the substrate
12
to the rinse chamber
50
. The rinse chamber
50
can include a plurality of opposing spray bars
51
, each having a plurality of nozzles
52
for directing a spray of the rinsing solution
53
onto the substrate
12
. The rinse chamber
50
shown in
FIG. 1
can simultaneously accommodate two substrates
12
positioned upright in adjacent bays
57
.
A third approach to removing particulate matter from the substrate
12
is to remove the substrate from the polishing pad
41
and place the substrate
12
on a separate buffing pad (not shown). The buffing pad then moves relative to the substrate and may also be supplied with a rinsing solution to convey the particulate matter away.
After the substrate
12
has been planarized and rinsed, the polishing pad
41
can be conditioned to restore its ability to planarize additional substrates. Accordingly, the planarizing machine
10
can include a conditioner
70
that removes polishing pad material from the planarizing surface
42
to expose new polishing pad material. The conditioner
70
can include an abrasive disk
71
for mechanically roughening the planarizing surface
42
of the polishing pad
41
. The conditioner
70
can also include a conditioning fluid source
72
that supplies conditioning fluid to the polishing pad
41
for chemically conditioning the planarizing surface
42
of the polishing pad
41
.
Planarizing processes must consistently and accurately produce a uniformly planar surface on the microelectronic substrate
12
to enable precise fabrication of circuits and photo-patterns. As the density of integrated circuits increases, the uniformity and planarity of the substrate surface is becoming increasingly important because it is difficult to form sub-micron features or photo-patterns to within a tolerance of approximately 0.1 microns on nonuniform substrate surfaces. Thus, planarizing processes must create a highly uniform, planar surface on the substrate.
One drawback with the conventional methods discussed above is that they may not create a sufficiently planer surface on the substrate because particulates may remain attached to the substrate as a result of contact between the substrate
12
and a variety of chemical solutions during and after planarization. For example, in one conventional method the planarizing solution is an ammonia-based solution, and the rinsing and conditioning fluids are deionized water. Each chemical solution may have different chemical characteristics and sequentially exposing the microelectronic substrate
12
to different chemical solutions may cause particulates to adhere to the surfaces of the substrate. These particulates may damage the wafer during subsequent polishing and handling steps, or may interfere with subsequent processing steps, such as masking and etching. Furthermore, the particulates may become incorporated into the devices formed on the substrate, potentially causing the devices to fail.
In the competitive semiconductor and microelectronic device manufacturing industries, it is desirable to maximize the throughput of finished substrates. Accordingly, a further drawback with the conventional processes, described above is that they may require additional time to remove the particulates from the substrate. The additional time can be required because the substrate has additional particulate adhered to it as a result of exposure to various chemical solutions.
SUMMARY OF THE INVENTION
The present invention is directed toward methods and apparatuses for processing a microelectronic substrate. In one em
Hudson Guy F.
Sharples Judson R.
Zacharias Kenneth F.
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